1. Field of the Invention
The present invention relates to a still video device, and more particularly relates to a device for controlling a still video device in order to eliminate or reduce the effect of blooming in a still image produced by a still video device.
2. Description of the Related Art
In a conventional still video device, electrical image signals corresponding to an object are formed by a charge-coupled device (CCD), processed, and are then recorded as a still image on a recording medium such as a memory card. Each signal formed by the CCD has a value corresponding to the luminance of a portion of the object. When the object includes a high luminance portion, smearing may occur extending in upward or downward directions from the resulting high luminance portion of the image. Accordingly, in order to prevent such smearing from occurring, residual electrical charges existing on a vertical transfer CCD are discharged through a horizontal transfer CCD to the outside of the device, by a so-called high speed discharge operation.
Some conventional still video cameras have a mechanism for adjusting an exposure value in accordance with the luminance of an object. Namely, when the object is photographed under a rear light condition, for example, by a photographer, an exposure compensation value (exposure adjustment value) having a positive value is added to an exposure value that was obtained by photometry, so that a distinct object image can be obtained.
As described above, when a high luminance portion exists in an image frame, the smear generated on the frame can be removed. However, when an exposure compensation value having a positive value is added, the high luminance portion acquires an effectively higher luminance. Therefore, electric charges that are overflowing from the high luminance portion enter upper and lower portions thereof (i.e., move along the electric charge transfer direction in the vertical transfer CCD). As a result, blooming occurs which comprises bright stripes that extend in upward and downward directions from the high luminance portion, thereby deteriorating the image quality.